Retention time of chromium-labelled feed particles and of water in the gut of sheep given hay and concentrate at maintenance

Abstract

1. Sheep were given a diet of 400 g chopped grass hay/d and 500 g crushed barley/d in three equal meals. The mean retention time in the whole gut (MRT) and the rumen retention time (RRT) of chromium-labelled feed particles and of water were estimated from marker concentrations in faecal samples. 2. MRT of Cr-labelled hay (Cr-H), barley hulls (Cr-Bh), crushed peas ( Pisum sativum ) (Cr-CP) and rapeseed meal (Cr-RSM) were 53.5, 52.3, 44.3 and 37.0 h respectively when estimated from total faecal collections. The estimates obtained from spot samples of faeces were almost identical. 3. RRT of Cr-H, Cr-Bh, Cr-CP, Cr-RSM (Expts 1, 2 and 3) and Cr-labelled cottonseed meal (Cr-CSM) was 35.9, 36.7, 25.3, 18.8, 19.8, 22.8 and 25.3 h respectively. 4. The Cr-labelled feed particles showed marked variations in density in water (D ω ). However, both MRT and RRT were closely related to D ω , (r—0.88 and —0.95 respectively). 5. Rumen outflow rates of Cr-RSM in individual animals were related to the rumen outflow rates of water (r 0.76).